Method and apparatus for producing a hydrogen-containing gas

Abstract

A process and apparatus for producing a hydrogen-containing gas in a reformer where a furnace, which is independent of the reformer, heats the effluent from a prereformer prior to reacting the prereformer effluent in the reformer. The prereformer effluent may be heated in a heat exchange tube in the furnace where the heat exchange tube is positioned in the furnace to preclude direct radiation from any flames in the furnace thereby preventing local overheating of the heat exchange tube and preventing carbon formation in the heat exchange tube. Fuel and oxidant gas may be introduced into the furnace with significant excess oxidant gas, having a stoichiometric ratio of 1.8 to 2.8 for controlling the temperature of the heat exchange tube.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 11 / 220,079, filed Sep. 6, 2005, the specification and claims which are incorporated by reference and made a part of this application.BACKGROUND OF THE INVENTION[0002]In hydrocarbon reforming, a hydrocarbon feedstock and steam are reacted catalytically in a reformer furnace to form a synthesis gas comprising hydrogen and carbon monoxide. The reforming furnace is a critical component of hydrogen production facilities and plants which use synthesis gas to produce methanol and ammonia, and can account for almost half of the operating costs and energy expenditures of such installations.[0003]A typical reforming furnace comprises a fired radiant section, a transition section, and a convection section. Tubes filled with a reforming catalyst, i.e. reformer tubes, are disposed in the radiant section. The reforming catalyst is typically nickel on an alumina support. A hy...

AI Technical Summary

Benefits of technology

The present invention relates to a process and apparatus for producing a hydrogen-containing gas. The technical effects of this invention include improved energy efficiency, reduced emissions, and improved production of hydrogen-containing gas. The process involves combusting a first fuel and a first oxidant gas in a reformer to form a first combustion product gas mixture and heat the plurality of reformer tubes. A heated feed is then reacted in an adiabatic reactor containing a reforming catalyst to form an intermediate product gas mixture. The intermediate product gas mixture is then heated in a furnace by indirect heat transfer from the first combustion product gas mixture and the second combustion product gas mixture to form the hydrogen-containing gas. The heated intermediate product gas mixture may not be further heated in the furnace. The process may also involve heating the feed by indirect heat transfer from the first combustion product gas mixture to the feed. The second fuel and oxidant gas are introduced into the furnace with a stoichiometric ratio of 1.8 to 2.8. The heated intermediate product gas mixture has a temperature ranging from 600°C to 700°C. The apparatus includes a reformer and a furnace with heat exchange tubes and a burner. The heat exchanger between the outlet of the first heat exchange tube and the inlet manifold of the reformer tubes is located in the furnace to preclude direct radiation from the flame generated by the burner. The reformer may have a second section containing a second heat exchange tube, and the furnace may contain a third heat exchange tube. The technical effects of this invention include improved energy efficiency, reduced emissions, and improved production of hydrogen-containing gas.

Problems solved by technology

Operating the radiant section in this way requires increased maintenance and shortens the reformer tubes useful life.

Increasing the heat duty provided by the radiant section can also lead to coke formation in the reformer tubes.

A conventional reforming process such as that illustrated in FIG. 1 can only achieve a preheat temperature of around 500° C. to around 600° C. due to the risk of carbon formation from the heavy hydrocarbons present in the feedstock.

The preheat and prereforming process designs described above prove unsuitable for expanding the production capacity of an existing reformer above around 25% of existing capacity because they are constrained by the energy available in the flue gas, the radiant section firing duty, convection section space limitations, and the overall plant heat balance.

This makes it difficult to regulate the reheat temperature of the prereformed gas.

Installation of a prereformer in the transition section of an existing reformer is very expensive.

The reformer must be taken off-line, thereby disrupting the output of all associated facilities.

Limited space in the convection section often precludes installation of an adequately-sized prereformer.

Further, the convection section coil design may interfere with the positioning of prereformer tubes in the convection section.

These problems can be compounded by the fact that heat in the flue gas coming from the reformer radiant section may be inadequate to heat both the convection section coils and the prereformer tubes.

In such cases, installing a prereformer in the convection section could disrupt the energy balance of the reformer and all associated plants.

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